SYNTHESIS AND PHYSICAL PROPERTIES OF SOME NEW OXYFLUORIDES

Open Access
Author:
Kwak, Jung eun
Graduate Program:
Chemistry
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Tom Mallouk, Thesis Advisor
Keywords:
  • reductive fluorination method
  • oxyfluorides
  • mixed-valence layered perovskites
  • semiconducting binary oxides
Abstract:
The solid-state reductive fluorination of Dion-Jacobson phase layered perovskites RbLaNb2O7 and KCa2Nb3O10 was studied by using poly(tetrafluoroethylene) (PTFE, monomer unit CF2) as a reductive fluorinating agent. This method was previously discussed in a preliminary report on the mixed-valence layered oxyfluorides RbLaNb2O6F, KCa2Nb3O9-xFx, and NaYTiO4-xFx (Kobayashi, Y.; Tian, M.; Eguchi, M.; Mallouk, T. E. J. Am. Chem. Soc. 2009, 131, 9849). X-ray diffraction patterns of the fluorination product of perovskite oxide RbLaNb2O7 suggested that we successfully made electrically conducting, ion-exchangeable and air-stable mixed-valence layered perovskite oxyfluorides by the PTFE route. However, the electronic conductivity of this product was several orders of magnitude lower than that previously reported, and the material was unstable when ion-exchanged with acid and exfoliated with the bulky base tetra(n-butylammonium) hydroxide. Thus, further study of reductive fluorination in the RbLaNb2O7 system and with other layered perovskites is needed. A new reductive fluorination method for binary oxides, especially semiconducting binary oxides, was developed by using perfluorodecalin (C10F18) as a gas-phase fluorinating agent. Semiconducting binary oxides were also reacted with PTFE under the same conditions as with layered perovskites but in most of cases they showed little or no reduction. As an alternative vapor-phase fluorinating agent, perfluorodecalin (C10F18) were used to obtain oxyfluorides. The results of this method appear interesting because the fluorinated SnO2 product had low resistivity and low carbon residue. Thus, we plan to extend the new fluorination method developed with SnO2 to other semiconducting binary oxides such as GeO2, PbO, TiO2, ZrO2, V2O5, Nb2O5, Fe2O3, CuO, ZnO and In2O3. This method could in principle be applicable to the vapor phase reductive fluorination of other binary oxides, layered perovskite oxides and non-perovskite layered oxdes.